序列化到文件

NSDictionary *dict = @{@"text": @"Hello",
                       @"num": @3.14};

NSData *bin = [NSKeyedArchiver
    archivedDataWithRootObject:dict
    requiringSecureCoding:YES
    error:nil];

[bin writeToFile:@"data.bin"
    atomically:YES];
//data written to file